From Wikipedia on "Coherer""The coherer became the basis for radio reception around 1900, and remained in widespread use for about ten years. It saw commercial use again briefly in the mid 20th century in a few primitive radio-controlled toys that used spark-gap transmitter controllers."

Been researching Coherers (a primitive spark-era receiver) and wondered what the heck "mid 20th century" toy was controlled by a spark transmitter?

I made one stinkin' contact using my new OHR-100a turned down to about 750 mw and I was using a pretty good 40 meter antenna (at least for DX). Called several stations in the test but people didn't reply. Most of the signals were very weak here.

I know my radio gets out. I worked a Hungarian station a few nights ago. Conditions must have been terrible last night.

It's amazing that anyone was able to bridge the Atlantic with a coherer receiver and spark. I see on the web where a lot of people have recreated their own coherers and are easily able to get them to work, but only at very limited range, like across a room.

Crystal sets were invented around 1906. Hard to believe but a crystal would have been a gigantic improvement over the coherer's metal filings in a tube that had to be tapped after every code element.

Yep, I heard you. I think you were one of the guys I heard and got set to work (callsign in the log, zero-beat, break-in on) and then you went away. Happened a few times last night. I managed a grand total of three QSOs. Conditions were pretty rough.

I had my usual terrible QRN right around the QRP portion of 20 and the normal summer QRN all over 40. Nearly two hours of listening to that made me a little punch drunk. Can't wait for the next regular QRP sprint. QRPp is rough...in the summer anyway.

That was my first QRP effort since the 1992 ARRL CW DX contest which was a snap with ten meters wide open. Won the Zero district and made top ten in U.S. a real rarity for me. My only tough contact then was my lone JA on 80 meters.

Last night was much tougher for ONE CONTACT. I was only on 40, the only band my OHR radio will do. My those QRPp signals are weak! The final half hour I turned up the power to a full 5 watts but never heard any CQ NAs after that and lost interest.

Look for you next time. A couple of hours (and not much more) of QRP is fun.

2) There is some doubt about whether Marconi actually heard the "S" in 1901. Later tests were much more credible.

A coherer operator wouldn't hear (or record on paper tape) radio signals directly as a crystal set or modern receiver would A coherer operator hears current passing through clumped metal filings in the glass coherer tube. So it's impossible to tell a Morse "S" from three static crashes. I've wondered why Marconi used an "S" which is easily mimicked by nature rather than attempt a complex and historically appropriate phrase in the fashion of Morse and Bell.

After activation by RF the clumped filings are immediately un-clumped (or de-cohered) by the impact of an electromagnet similar to a door bell striker. I presume that coherers, like land-line sounders, can only do dits, and not dahs. So a code like American-Morse had to be used until the crystal detector arrived a few years later. Is that right?

Whether Marconi received signals from Europe that night is doubtful. But two-way radio across the Atlantic was fairly common within a few years.

"To conserve his dwindling resources, Marconi had Fleming purchase the largest used alternator available for Poldhu. Concerned and fearful of damaging this unit, they tuned its spark gap to the shortest possible duty cycle. This meant the sound of the Poldhu transmitter was not the characteristic “buzz-buzz-buzz” we are taught to expect of spark transmitters, but rather Poldhu produced a “click-clickclick” like a wireline telegraph sounder."

Guess I'm showing my age (66) but I had one as a kid. You had to keep pushing the xmit button to step thru three or four turning steps. I tried to "DX" with the thing by hooking a long wire to the xmitter output.......knocked me on my butt!!!!!!!!

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